This invention relates to thermal insulation, and particularly to improvements in gas impervious pouch structure for containing a porous mass of thermal insulation or such a porous mass and a charge of gas having a coefficient of thermal conductivity lower than that of air.
Pouch structures containing insulation or insulation and gas as described have been found useful as insulation units for installation in the walls and doors of refrigerator cabinets. Such units both facilitate handling of the insulation and enhance performance of refrigerator cabinets and the like within which they are installed. These insulation units also have been found useful for other home appliances, such as, for example, freezers and water heaters, as well as for residential and commercial building structures.
Fibrous insulation comprising glass fibers or the like, in combination with an insulating gas such as difluorodichloromethane, commonly known as F-12 refrigerant, and enclosed in pouch structures of materials that are both gas and moisture impervious have been used.
The prior art is believed to be best exemplified by the following patents:
______________________________________ Dybvig 2,817,124 12/57 Sorel 2,966,439 12/60 Simms et al 3,004,877 10/61 Gaugler 2,863,179 12/58 Gaugler et al 2,779,066 01/57 Stickel 3,264,165 08/66 Bolsolas 4,054,711 10/77 Dillon 2,939,811 06/60 Jacobs 2,817,123 12/57 Strong et al 3,179,549 04/65 Janos 2,745,173 05/56 ______________________________________
Dybvig, U.S. Pat. No. 2,817,124, discloses an insulating unit having two side by side compartments wherein the inner and outer walls of one compartment are comprised of Mylar coated on both sides with vapor deposited metal coating which in turn is coated with polyethylene, Saran or Hycar vinyl while the outer compartment is formed of polyethylene having pinholes of sufficient size to admit air.
Sorel, U.S. Pat. No. 2,966,439, discloses laminated products of normally thermoshrinkable polyvinylidene chloride film bonded in thermoshrunk condition to a normally dimensionally thermo-stable material such as fibrous sheet material.
Simms et al, U.S. Pat. No. 3,004,877, disclose heat insulating units for refrigeration cabinets comprising a porous mass and gas in a hermetically sealed bag formed of a multi-ply laminate including Kraft paper, Saran, Hycar vinyl cement and polyethylene.
Gaugler, U.S. Pat. Nos. 2,779,066 and 2,863,179, disclose heat insulating bags comprising double bags and double insulation and Freon gas comprising laminations of Mylar or vinyl chloride or vinyl acetate or Hycar vinyl; metal coating; Mylar or polystyrene; metal coating; Mylar or vinyl chloride or vinyl acetate or Hycar vinyl; Saran.
Stickel, U.S. Pat. No. 3,264,165, discloses insulating means comprising insulating material enclosed by Saran or a copolymer of vinyl chloride enclosed by Saran or a copolymer of vinyl chloride and vinyl acetate or Mylar adhered to a flexible closed-cell polyurethane film or multilayers of Kraft paper or foam; organic resin; metal coating; polyurethane foam; polyvinyl alcohol; metal coating; polyethylene.
Bolsolas, U.S. Pat. No. 4,054,711, discloses multilayer jacketing material for covering thermal insulation on pipes comprising a composite of metallized Mylar; adhesive; asbestos paper; glass scrim cloth; adhesive; polyvinyl fluoride film.
Jacobs, U.S. Pat. No. 2,817,123, discloses double bag constructions comprising an inner bag of laminated Mylar and Saran and an outer bag of fibrous insulation and polyethylene.
Dillon, U.S. Pat. No. 2,939,811, relates to heat-insulating units comprising hermetically sealed bags comprising deformable walls, a porous mass and gas wherein the bag comprises Saran, polyvinyl chloride, vinyl-nitrile rubber or polyethylene.
Strong et al, U.S. Pat. No. 3,179,549, disclose thermal insulating structures of the vacuum type comprising hermetically sealed containers having internal pressures of less than 100 microns mercury wherein the walls are low carbon steel and stainless steel.
Janos, U.S. Pat. No. 2,745,173, discloses vacuum insulation wherein the filler material is compressed before assembly and caused to retain its compressed form and wherein the walls of the structures are stainless steel or low carbon steel.
Prior art structures as represented by the above disclosures have been deficient in one or more aspects. Most of such constructions utilize Saran to meet moisture barrier problems and are thus accompanied by the problems generated by the shrinkability and tendency of Saran to become plastic at higher temperatures. Structures substituting or combining Mylar or other plastics have been subject to puncture by the fibrous insulating material. To overcome such problems, plastic film has been protected with metal coatings or polyurethane foam or relatively thick multi-ply laminations have been necessary or the multi-bag compartmented constructions have been proposed.
In U.S. Patent application Ser. No. 929,305 filed July 31, 1978 of Nicholas Sheptak and James E. Dewine, now U.S. Pat. No. 4,172,915 issued Oct. 30, 1979 improved unitary thermal insulating units are disclosed and claimed wherein the pouch is formed of a multi-ply laminate consisting essentially of an inwardly facing sealing layer of low density polyethylene; a layer of vinyl primer; a layer of metal foil; a layer of low density polyethylene; and an outwardly facing layer of Mylar or oriented polypropylene.